The size and price of the ESP wifi modules have quickly made them into one of the preferred building blocks for IoT devices. Unfortunately they are not particularly well suited for very low power ...

(Passive InfraRed sensor) A device used to detect motion by receiving infrared radiation. When a person walks past the sensor, it detects a rapid change of infrared energy and sends a signal. PIR ...

Figure 1 shows a way to control a light (or other 120-V ac appliance) with a passive-infrared (PIR) alarm sensor. The original concept was to turn a closet or shop light on whenever someone went into.